• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.384-384
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• 2017

In this study, the numerical investigation of nonlinear flow in a porous medium was carried out. The applied numerical model is ANSYS CFX which is a three-dimensional fluid dynamic model, and the verification of this model was carried out by using the experimental data obtained from Mayer et al works(2011). The experimental and numerical results of velocity and Reynolds number-friction coefficient relationship show relatively a good agreement. Based on the experimental results, we analysed numerically the velocity and Reynolds number-friction coefficient relationship with the variation of permeability, dynamic viscosity and porosity and quantitatively the variation by applying the best curve fitting for each case.

• Journal of the Korean Geotechnical Society
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• v.22 no.4
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• pp.5-10
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• 2006

A special finite difference method for nonlinear dynamic response analysis of semi-infinite foundation soil using mapping which transforms semi-infinite domain into finite domain is presented here. For the region of engineering interest, mapping is isometric, and fur far field, shrink mapping which transforms infinite interval into finite interval is adopted. At first, the responses of semi-infinite foundation soil with linear constituting model are computed, and compared with theoretical results and those of existing method. Good agreements are obtained among the results of the proposed method, Lamb's theory and FEM with extensive mesh model. Then the responses of infinite foundation soil are computed by the present method, using small and large mesh model. The results of small and large mesh models agree well with each other, demonstrating the effectiveness of the proposed method.

• Journal of Information Processing Systems
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• v.14 no.2
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• pp.455-468
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• 2018

The concepts of graph theory are applied to model and analyze dynamics of computer networks, biochemical networks and, semantics of social networks. The analysis of dynamics of complex networks is important in order to determine the stability and performance of networked systems. The analysis of non-stationary and nonlinear complex networks requires the applications of ordinary differential equations (ODE). However, the process of resolving input excitation to the dynamic non-stationary networks is difficult without involving external functions. This paper proposes an analytical formulation for generating solutions of nonlinear network ODE systems with functional decomposition. Furthermore, the input excitations are analytically resolved in linearized dynamic networks. The stability condition of dynamic networks is determined. The proposed analytical framework is generalized in nature and does not require any domain or range constraints.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.05a
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• pp.379-382
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• 2007

The proper orthogonal decomposition(POD) is used to the modal analysis of microcantilever of dynamic mode atomic force microscopy(AFM). The proper orthogonal modes(POM) are extracted from vibrating signals of microcantilever when it resonates and taps the sample. The POMs resemble the linear normal modes(LNM) of cantilever vibrating at each resonance frequency. Some of POMs in tapping microcantilever show quite different shapes from the POMs of the resonating microcantilever. Also this POMs can be applied to model for the complex nonlinear behavior of the dynamic mode AFM microcantilevers.

• Journal of the Korean Society for Railway
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• v.9 no.4 s.35
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• pp.461-466
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• 2006

In order to transport cargo rapidly and safely from the trans-Korean railway to the trans-Siberian railway having a different gauge, a gauge-changeable freight wagon can be used. Because the wagon is expected to run in South Korea, North Korea and Russia, it should have good dynamic performance in these railways. In this paper, the dynamic characteristics of a gauge-changeable freight wagon was analyzed numerically using ADAMS/Rail in each condition of the railways having different gauges and rail profiles. The wagon makes use of load sensitive friction damping and has highly nonlinear behaviour, which is modeled in detail as the full nonlinear dynamic model. It is shown that the running behaviour of the wagon is sensitive to changes in the rail gauge and profiles, however the assessment quantities from the point of view of safety, track fatigue and running behaviour are less than the limit valves.

• International Journal of Control, Automation, and Systems
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• v.6 no.4
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• pp.495-505
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• 2008

This paper describes modeling Voltage Sourced Inverter (VSI) type Flexible AC Transmission System (FACTS) controllers and control methods for power system dynamic stability studies. The considered FACTS controllers are the Static Compensator (STATCOM), the Static Synchronous Series Compensator (SSSC), and the Unified Power Flow Controller (UPFC). In this paper, these FACTS controllers are derived in the current injection model, and it is applied to the linear and nonlinear analysis algorithm for power system dynamics studies. The parameters of the FACTS controllers are set to damp the inter-area oscillations, and the supplementary damping controllers and its control schemes are proposed to increase damping abilities of the FACTS controllers. For these works, the linear analysis for each FACTS controller with or without damping controller is executed, and the dynamic characteristics of each FACTS controller are analyzed. The results are verified by the nonlinear analysis using the time-domain simulation.

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.1172-1177
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• 1993

Dynamic characteristics of a hydraulic power supply are studied theoretically and computationally. The transfer function between the supply pressure and the load flow is derived considering relief valve dynamics, accumulator dynamics, and flow line dynamics. Frequency responses and time responses are obtained in many conditions using the transfer function and nonlinear mathematical model respectively.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.10
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• pp.1034-1042
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• 2009

In this paper, the magic formula model was applied for a friction damper in a drum-type washing machine. To describe characteristics of the hysteretic damping force, Physical tests were first carried out to get experimental results using an MTS machine. Then, parameters for the magic formula model were determined from the experimental curves. The ADAMS and MATLAB programs were used for the multibody modeling of the damper and process for parameter identification. The model of drum-type washing machine was applied for a dynamic model of friction damper, in which the accuracy of the proposed damper model was verified.

• International Journal of Fuzzy Logic and Intelligent Systems
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• v.13 no.4
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• pp.277-283
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• 2013

In this study, we propose a novel method for modeling dynamic hysteresis. Hysteresis is a widespread phenomenon that is observed in many physical systems. Many different models have been developed for representing a hysteretic system. Among them, the Duhem model is a classical nonlinear dynamic hysteresis model satisfying the properties of hysteresis. The purpose of this work is to develop a novel method that expresses the local dynamics of the Duhem model by a linear system model. Our approach utilizes a certain type of fuzzy system that is based on Takagi-Sugeno (T-S) fuzzy models. The proposed T-S fuzzy Duhem model is achieved by fuzzy blending of the linear system model. A simulated example applied to shape memory alloy actuators, which have typical hysteretic properties, illustrates the applicability of our proposed scheme.

• Water for future
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• v.28 no.3
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• pp.113-122
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• 1995

A nonlinear wave routing model is suggested for the routing of floods in the natural open channel networks. For the optimization of parameter of the proposed routing model, parameter adjustment is executed through the proposed objective function. The model treats backwater effect form upstream and downstream ends. Solution of formulated model is made possible on computer by adopting a nonlinear finite-difference scheme for the numerical analysis based on a combination of Lax-Wendroff scheme and Burstein-Lapidus modification. Comparison of the results of the proposed model to those of actual hydrograph and dynamic wave routing model denotes that the proposed model is as accurate as actual runoff hydrograph and faster the computer time than the dynamic wave routing model.